An airport transit visa is applicable for the people who are just transiting the Schengen territory and who will not leave the transit area of the airport.

If you are going to wait for a few hours at the airport's international transit area, you will need to apply for an airport transit visa. However, hotel accommodations are only available outside the transit area and you would need a regular tourist visa if you want to stay in the hotel overnight.

If you don't have a confirmed onward flight from Germany and therefore require an airport transit in Germany, you need to apply for a regular tourist visa and not for an airport transit visa.

If your arrival and departure are from 2 different airports, you will require a regular transit visa and NOT just
an airport transit visa.

The airport transit visa is issued by the consulate of the country where the transit airport is located.

If you travel from the USA via the French airport to enter another Schengen country or
if you have a second transit in another Schengen country airport,

The passport control is done at the first point of entry in the Schengen territory. All flights between two or more Schengen countries are considered domestic flights. Depending upon your citizenship, you may need a
transit visa.

If you transit through a French airport and if you need a visa for the Schengen country
which is your main destination, you must apply for a short stay visa at the consulate representing
that country.

If you travel from the USA via a French airport to enter Switzerland by Bale or Geneva,
you have to apply for a transit visa
depending upon your country of citizenship.

FAQ

Q:
I am a citizen of India. I would be traveling from Mumbai to Washington DC through Paris. I will stay in the airport (or in the airplane) during 3 hour stop at the airport in Paris. I will not be going out of the airport. Do I need an airport transit visa?

A:
If you have a valid (un expired) U.S. visa stamped in your passport or if you have a green card,
you don't need airport transit visa. Otherwise, you do.

Q:
I am a citizen of India. I have a valid F-1 visa stamp in my passport. I had applied for a change to
the H-1B visa through my employer. Now I am going to India to get an H-1B stamped in my passport.
I will be traveling to Chennai through Paris. I will not be going out of the airport. Do I require an
airport transit visa?

A:
No, as long as you have a valid (un expired) U.S. visa stamped in your passport,
you don't need an airport transit visa, even if your legal status has changed.